Process for the manufacture of 1-phenyl-2.3-dimethyl-4-dimethylamino-5-pyrazolone



Patented Mar. 31,1925. 1,531,286

UNITED STATES PATENT OFF-ICE.

PROCESS FOR THE. MANUFACTURE PYRAZOLONE.

Io Drawing. Application filed November 11, 1922. Serial No. 600,198.

To all whom z'fimay concern: methyl-4-aminio-5-pyrazolone is obtained Beit known that I, JULIUS HOFFMANN, a by treating1-phenyl-2.3-dimethyl-pyrazof citizen of Switzerland, and a resident oflone with nitrous acid, reduction of. the re- Hongg, near Zurich,Switzerland, have in- Sulting nitroso compound with bi-sulphite 5 vented.eertain new and useful Improveand (siplitting u of the'sulphaniino'comments in a Process for the Manufacture of poun with acidf l-Phenyl-2.3-Dimethyl-4-Dimethylamino-5- I have found that for themanufacture of Pyrazolone, of which the following is al-phenyl-2.3-dimethyl-4-dimethylamino-5 specification. pyrazo one it'isnot necessary to start from My invention relates to a process for the1phenyl-2.3-dimethyl 4-amino-5-pyrazal0ne, manufacture'of1-phenyl-2.3-dimethyI+4-diwhich is but diflicultly obtained in puremethylamino-5-pyrazolone which consists in form, but that the easilycrystallizing sul- OE 1-?HENYL-2.8-DIKETHYL-4-DIMETH?LAMINO-5- vallowing formaldehyde in the presence of phamino compound may be used.By treatformic acid to act upon 1-phenyl-2.3-diing1-phenyl-2.3-dimethyl-4;-sulphamino-5r methyl-4-sulphamino-5-pyrazolone.pyrazolone'with formaldehyde in the pres- K. Hess (Berichte derDeutschen. Ohemence of formic acid the dimeth lated comischenGesellschaft, vol. 48 (1915) (page pound is obtained'and the sulp 0group is 1888) has shown, that the usual methylatspllt up at the sametime. One obtains by ing agents, such methyliodide, methylchlothisprocess a considerable reduction of ride, etc., may in many cases beadVa-ntalabor and the l-phenyl-2.3-dimethyl-4- geously substituted byformaldehyde used in dimethylamino-fi-pyrazolone thus prepared thepresence of formic acid. This proces is purer than thatmanufacturedaccording may also be employed with good success for to other processesand the yield is excelmethylating 1-phenyl-2.3-dimethyl-4-aminolent. Y5- yrazolone.

t is a known fact that,1-phenyl-2.3-difollows:

L J} om cm-N o +aomo-0mo +oo|+mso.

Example, from the methylatin mixture by stirring v A with benzol and adition of an excess of An, aqueous "solution of 1-phenyl-2.3.-disodiumhydroxide solution. I The 'furth methyl-4-sulphamino-5-pyrazo one,obtained purification of the product thus obtained is from 188 parts of1-phenyl-2.3-dimethylperformed in the usual manner. 7

pyrazolone, is slowly added, over a period of I claim: about ten hours,to a mixture of 213 parts The process .for the manufacture of 1- offormaldehyde (36 per cent) and 150 parts phenyl 2.3 dnnethyl 4-dimethy1amino-5-. of formic acld (80 per cent), which latter pyrazolonewh1ch conslsts 1n allowing formixture is constantly stirred and kept, ata maldehyde 1n the presence of formic acid to temperature slightly abovethe boiling point. not upon 1-pheny1-2.3-d1methyl4-sulpham Thereafterthe heating is continued for an -PX hour, the end of the methylatingrocess be- In WltfleSS where f I have hereunto set ing indicated by thefact that car onic acid y handno longer forms; any excess offormaldehyde JULIUS HOFFMAN'N.

may be recovered as a dilute solution. Witnesses:

After cooling the 1-phenyl-2.3-dimethy1-, Wmunc Grimm,4=-dimethylamino-5-pyrazol0ne is extracted Thereaction is believed totake place as I

